EC-COUNCIL EC-COUNCIL Certifications 212-81 Questions & Answers

• Question 131:

  Which one of the following attempts to hide data in plain view?

  A. Cryptography

  B. Substitution

  C. Steganography

  D. Asymmetric cryptography

  Correct Answer: C

  Steganography https://en.wikipedia.org/wiki/Steganography Steganography is the practice of concealing a file, message, image, or video within another file, message, image, or video. The word steganography comes from Greek steganographia, which combines the words steganos , meaning "covered or concealed", and -graphia meaning "writing".

• Question 132:

  What is the basis for the difficulty in breaking RSA?

  A. Hashing

  B. The birthday paradox

  C. Equations that describe an elliptic curve

  D. Factoring numbers

  Correct Answer: D

  Factoring numbers

  https://en.wikipedia.org/wiki/RSA_(cryptosystem)

  RSA (Rivest-Shamir-Adleman) is a public-key cryptosystem that is widely used for secure data transmission. It is also one of the oldest. The acronym RSA comes from the surnames of Ron Rivest, Adi Shamir, and Leonard Adleman, who

  publicly described the algorithm in 1977. An equivalent system was developed secretly, in 1973 at GCHQ (the British signals intelligence agency), by the English mathematician Clifford Cocks. That system was declassified in 1997.

  In a public-key cryptosystem, the encryption key is public and distinct from the decryption key, which is kept secret (private). An RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value.

  The prime numbers are kept secret. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers.

• Question 133:

  What size key does Skipjack use?

  A. 128 bit

  B. 56 bit

  C. 80 bit

  D. 256 bit

  Correct Answer: C

• Question 134:

  In a ______ the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

  A. Information deduction

  B. Total break

  C. Instance deduction

  D. Global deduction

  Correct Answer: D

  Global deduction https://en.wikipedia.org/wiki/Cryptanalysis Global deduction -- the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

• Question 135:

  Terrance oversees the key escrow server for his company. All employees use asymmetric cryptography to encrypt all emails. How many keys are needed for asymmetric cryptography?

  A. 2

  B. 4

  C. 3

  D. 1

  Correct Answer: A

  https://en.wikipedia.org/wiki/Public-key_cryptography Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.

  In such a system, any person can encrypt a message using the receiver's public key, but that encrypted message can only be decrypted with the receiver's private key.

• Question 136:

  Which of the following encryption algorithms relies on the inability to factor large prime numbers?

  A. RSA

  B. MQV

  C. EC

  D. AES

  Correct Answer: A

• Question 137:

  Which of the following was a multi alphabet cipher widely used from the 16th century to the early 20th century?

  A. Atbash

  B. Caesar

  C. Scytale

  D. Vigenere

  Correct Answer: D

• Question 138:

  If you use substitution alone, what weakness is present in the resulting cipher text?

  A. It is the same length as the original text

  B. It is easily broken with modern computers

  C. It maintains letter and word frequency

  D. It is too simple

  Correct Answer: C

  It maintains letter and word frequency https://en.wikipedia.org/wiki/Frequency_analysis Frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers. Frequency analysis is based on the fact that, in any given stretch of written language, certain letters and combinations of letters occur with varying frequencies. Moreover, there is a characteristic distribution of letters that is roughly the same for almost all samples of that language. For instance, given a section of English language, E, T, A and O are the most common, while Z, Q, X and J are rare. Likewise, TH, ER, ON, and AN are the most common pairs of letters (termed bigrams or digraphs), and SS, EE, TT, and FF are the most common repeats. The nonsense phrase "ETAOIN SHRDLU" represents the 12 most frequent letters in typical English language text. In some ciphers, such properties of the natural language plaintext are preserved in the ciphertext, and these patterns have the potential to be exploited in a ciphertext-only attack.

• Question 139:

  Which one of the following is an example of a symmetric key algorithm?

  A. ECC

  B. Diffie-Hellman

  C. RSA

  D. Rijndael

  Correct Answer: D

  Rijndael https://en.wikipedia.org/wiki/Advanced_Encryption_Standard The Advanced Encryption Standard (AES), also known by its original name Rijndael. The algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data.

• Question 140:

  ____________cryptography uses one key to encrypt a message and a different key to decrypt it.

  A. Secure

  B. Asymmetric

  C. Stream

  D. Symmetric

  Correct Answer: B

  Asymmetric https://en.wikipedia.org/wiki/Public-key_cryptography Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.